Settlers platted a townsite in Section 14 of the Leavenworth area in 1857, and the next year Dr. J. B. Calkins established the post office and became its first postmaster. Leavenworth Township was legally organized on April 16, 1859, with seven elected officers: Luther Whiton as chair; Isaac Bandy and Seth Henshaw as supervisors; George Charnock as clerk; Peter Kelly as assessor; and G. W. Maffett and C. R. Putnam as constables. During the Dakota Conflict of 1862, settlers fled the area, then later returned to build the new village of Leavenworth in Section 27. The settlement grew to include a blacksmith shop, general store, sawmill, flour mill, shoemaker, physician, and druggist, but its hopes for expansion faded when the railroad bypassed Leavenworth in the 1870s, and the new village was never incorporated. Today, the Church of the Japanese Martyrs, erected in the late 1860s, remains from one of Brown County's earliest settlements.